There have been several recent applications of derivative information to other related problems in stellarator design. The FOCUS [1]} and FOCUSADD [2]} codes optimize coil shape to be consistent with a given plasma boundary with gradients obtained from analytic and automatic differentiation methods, respectively. Our work is distinct from the FOCUS approach, as we use gradients to optimize properties of the equilibrium rather than using gradients to optimize coils in order to match the boundary of a given equilibrium. Adjoint methods have recently been applied to directly optimize coils for quasisymmetry near the magnetic axis in a vacuum field [3]}. In contrast to this work, our approach can be applied to optimize equilibria with arbitrary pressure. Furthermore, we have developed adjoint methods for direct optimization of coil shapes for properties of an MHD equilibrium [4]}, [5]}, although its application to optimization is not presented in this work. Adjoint methods have also been used to optimize the local magnetic field for neoclassical properties [6]} and the coil winding surface for properties of the current potential [7]}.
